the way you described the feces makes me suspect blood as well. A couple of years ago I felt something rip inside my abdomen. Although I had not eaten pumkin seeds, my diet was pretty lousy back then. The ripping was the creation of a diverticuli in my large intestine that started bleeding. The next morning, I past stool that was black just like you described. Alos it sort of stinged as it passed by the anal wall. I don't know if that happened to you but you do need to find the source of the black feces.